Known techniques of mounting electronic parts to a surface mount circuit that is fabricated on a substrate such as a printed circuit board or a flex circuit include the use of alignment holes in the substrate, or utilize fixturing that is used at the time of attachment of the part. As an example of the use of alignment holes in the substrate, pins that are a portion of the electronic part fit into the alignment holes during and after attachment of the electronic part to the substrate. Another example of the use of alignment holes is when fixturing pins are temporarily passed through holes in both the electronic part and the substrate. As another example of fixturing, a specially made tool can be make to align a flat, flexible liquid crystal display cable to a printed circuit board during a heat seal process. Such a fixture can, for instance, be made to align itself to edges of the board and edges of the cable. As yet another example of fixturing, indicia on the cable can be manually aligned by an operator using optical magnification aids during the heat seal process for the flat cable. Each of these approaches, although successfully employed in the past, has problems that are exacerbated as circuits continue to be designed smaller in order to achieve smaller, better products. One of the methods used to achieve smaller circuits is to using higher density circuit interconnections, which makes the required alignment of electronic parts to the substrate more critical.
In the first example of alignment methods, holes in the substrate take up an increasing portion of substrate surface area as circuits become smaller, because the pins used with the holes must be large enough to withstand the forces involved when they are inserted. Furthermore, there are practical limits to the accuracy of alignment of the pins to the holes. In other methods described above, the use of edges of the substrate and cable lead to inaccuracy caused by the tolerances in aligning the interconnects to the edges. Finally, alignment using human operators has lower practical limits that lead to inaccuracies.
Thus, what is needed is an improved method of aligning parts attached to a surface mount circuit.